Preparing ammonium polyacrylates

ABSTRACT

POLYACRYLATES ARE PREPARED IN AQUEOUS SOLUTION UNDER SPECIALLY CONTROLLED REACTION CONDITIONS TO PRODUCE EFFICIENT FLOCCULANTS. AMMONIUM ACRYLATE TO POLYMERIZED AT A MONOMER CONCENTRATION WITHIN THE RANGE FROM ABOUT 10 WEIGHT PERCENT OF THE POLYMERIZATION SYSTEM UP TO THE MONOMER SATURATION LEVEL, IN THE PRESENCE OF AT LEAST 0.1 WEIGHT PERCENT OF AMMONIUM HYDROXIDE. THE UPPER LIMIT ON THE AMOUNT OF HYDROXIDE EMPLOYED WILL RANGE DOWNWARDLY FROM ABOUT 15 WEIGHT PERCENT TO APPROXIMATELY 5 WEIGHT PERCENT FOR MONOMER CONCENTRATIONS FROM 10 TO 40 WEIGHT PERCENT RESPECTIVELY. FURTHER IMPROVEMENT IN POLYMER PROPERTIES IS ACHIEVED BY THE INCORPORATION OF AT LEAST ABOUT 1 WEIGHT PERCENT, BASED ON THE WEIGHT OF POLYMERIZATION SYSTEM, OF AN ALKALI METAL SALT.

United States Patent 3,658,771 PREPARING AMMONIUM POLYACRYLATES Henry Volk, Bay City, and Percy Jay Hamlin, Midland,

Mich., assignors to The Dow Chemical Company, Midland, Mich. No Drawing. Filed Jan. 14, 1969, Ser. No. 791,193 Int. Cl. C02b 1/20; C08d 1/04; C08f 3/46 US. Cl. 260 -80 M 9 Claims ABSTRACT OF THE DISCLOSURE provement in polymer properties is achieved by the in corporation of at least about 1 weight percent, based on the weight of polymerization system, of an alkali metal salt.

Because it is readily polymerized and used extensively in polymerization reactions, acrylic acid has been the subject of numerous polymerization studies. Usually this monomer is polymerized as an acid. Previous studies have shown that increasing the pH of the acrylic acid polymerization system decreases both the degree and rate of polymerization. See for example, Kogyo K'agaku Zasshi, Journal Chemical Society, Japan, Industrial Chemical Section, volume 58, pages l94l96 (1955).

Although acrylic acid can be polymerized to high molecular weight, flocculant grade polymers in the acid form, it is necessary in the processing of the polymerizate to mix a neutralizing reagent with the polymer gel. This is a difficult physical operation inasmuch as the aqueous polymerizates are very viscous and not readily mixed with other reagent, such'as ammonium hydroxide;

It would be particularly desirable to provide an improvide process for the preparation of ammonium polyacrylates. Especially desirable would be polymers of this nature characterized by high molecular weights and flocculation utilities. A further object is to provide a polym.

erization process which produces such polymers directly.

The instant invention is directed to the above ends and involves polymerizing an alkali metal or ammonium acrylate, or methacrylate, in water solution under especially controlled reaction conditions.

In the practice of the polymerization process of the invention, monomer concentration is maintained within the range from about 10 weight percent of the aqueous polymerization charge up to the monomer saturation level, preferably from about 20 to about 40 weight percent of the aqueous polymerization charge. To this solution is added enuogh ammonium hydroxide to provide at least 0.1 percent by weight thereof based on the weight of the monomer solution. Depending upon the monomer concentration, the upper limit on the amount of hydroxide added will range from about to about 5 weight percent, based on the total weight of the system, as the monomer concentration increases from about 10 to about 40 weight percent. Somewhat lower amounts of the hydroxide are desirable as the monomer saturation level is approached. The temperature of the reaction sys- 3,658,771 Patented Apr. 25, 1972 tem is maintained within the range from about 0 up to about 100 C., preferaby from about 25 to about 60 C. A pressurized polymerization vessel is employed at the higher temperatures to prevent escape of ammonla.

Although the process of the invention is essentially directed to the preparation of homopolymers of the ammonium acrylates, e.g., ammonium acrylate and methacrylate, alkali metal acrylates and methacrylates, as well as small amounts of other monomers compatible with the polymerization charge can be included in the polymerization system. Normally comonomers, i.e., monomers other than ammonium or alkali metal acrylates, will comprise less than about 25 weight percent of the monomer charge. Examples of suitable comonomers include sodium styrene sulfonate, sodium ethylene sulfonate, 2-sodioethyl acrylate, vinyl acetate and maleic acid, and the like. In general, any anionic or nonionic monomer which is soluble in the polymerization system and is not adversely affected by the excess ammonia can be copolymerized with the acrylates in accordance with the invention.

Further improvement in the above described polymerization process is achieved by introducing into the polymerization system at least about 1 percent by weight of an alkali metal or ammonium salt such as ammonium, sodium or potassium chloride or sulfate. Such salts yield polymers of even higher molecular weight and greater flocculation efiiciencies. These salts are useful at concentrations up to and exceeding the saturation level for the given system.

The above described recipes are polymerized by known techniques. Most conveniently the reaction is carried out as a solution polymerization reaction in water. Alternate modes include suspension and emulsion polymerization techniques whereby a monomer solution is first prepared and then either suspended or emulsified in a water immiscible liquid such as an aromatic or aliphatic liquid hydrocarbon.

Initiation ofpolymerization is accomplished by purging the monomer system of inhibitory oxygen and applying suitable catalytic means, such as chemical free radical catalysts or high energy irradiations, including X-rays, gamma rays and high energy electrons. Suitable chemical catalysts include sodium persulfate, potassium persulfate, ammonium persulfate, azobisbutyronitrile, tertiary butylhydroperoxide and in general any of the peroxidic acid polymerization initiators not adversely alfected by the high pH. Also operable are the redox initiator systems which involve the use of a reducing agent conjunctively with the oxidizing reagent.

Following completion of the polymerization reaction, the polymer is recovered by any convenient technique. When the polymerization is conducted in aqueous solution, the polymer may be recovered as by drum drying the polymerizate. Emulsion and suspension polymeriza tion systems are well adapted for removing water by azeo tropic distillation followed by a liquid-solids separation, as by filtering.

Polymers prepared in accordance with the invention are characterized by high molecular weights and thus good flocculation utilities. Since molecular weight determinations are time consuming, a first approximation 3 The instant invention will be further illustrated by reference to the following specific embodiments.

EXAMPLE 1 and fluocculation properties, increased conversion to polymer did result.

Although the invention has been illustrated by solution polymerization techniques, it should be understood y disfillhd S/ acifl in an amount of 765 5 that other modes of polymerization may incorporate the gagsltvlaxsmnggglmwfigrkagollltifriso; fiail tefi aig ilgnprovements and advantalgles of th; igstalt invention. or instance, mverse em sion an ea sus nsion the mixture was charged to a one liter resin flask equlpped polymerization techniques may be carried out filming with a stirrer, nitrogen sparger, gas outlet and thermommonomer solutions in which the monomer concentrw etch rfimoved from 19011011161 by tionandsolution pH are adjusted in accordance with the spal'gmg with g zix gh f df gf i parameters of the instant invention. Basically, in these room temperat r Y 6 a hon 11 3 me F polymerization techniques the monomersolution is susfite an amount of percent 0 owe y Potasslum pended in a heat transfer medium with either an emulsipeisulfate m an of h 531d pm'centages fying or polymeric suspending agent. Details as to such g z g s g g gi were 15 suspension techniques are set forth in US. Pats. 3,211,708,

3,278,506 an 3284,393. polymerization systems contalnmg different levels of Depending i the particular polymerization tech ammonium hydroxide. Polymerization was carried out n1-que utilized the polymer may be simply recovered at amblent P temperature and the.,polymgnzates from the polymerizate as by drying the polymerizate. to lyzed for resldual monomer. From this data, the conver recover the polymer 801i ds More conveniently p igz g monomer to polymer were calculated for each cipitation and, in the instance of the emulsion and sus- The polymers were isolated from the polymerizates by i zn f f z gfifiga g gfi gggi gz g i gg 3 23; precipitation with methanol. Volatiles were removed by p y g y Po y r from the polymerization medium may be employed to re. drying at about 40 -50 C. in a vacuum oven. The ms 25 cover 01 mr Solid It Should b understood ho e r cosity of the dried product was determined using an th t p f 1 i t i w i Ostwald viscometer to measure 0.4 percent-by volume Separa p0 l S l 5 18 no necessary 0 Polymer solutions in 05 normal sodium chloride. their useful appllcatlon. For instance, the polymer gels The activity of the polymers as flocculants was deterand SHSPIBIISIOHS thelreotmn be directly enployed to ppemined by flocculation tests on a 10 percent by volume Pare a utlons an i i slurry of montmorillonite clay in a 0.6 normal sodium a e X F systems can 6 aPP led as hydroxide solution. The clay suspension was' contained flocculanfs dllutlon' within a stoppered 100 milliliter graduate. The suspension What clalmed was treated with an applicating solution containing 0.025 1- A method 9 P P h alkah metal and ammonium weight percent of dissolved polymer at doses of 1, 2 and 5 P l 71 Whlch comprises 3 milliliters. After mixing the polymer with the clay susformmg an q s solution m g from pension according to a standard procedure, which inahhht P t by Y to about 196mmt y volved rotating the graduate three times after introduc- W i dissolved alkah meial 0f ammom'hm yl tion of the polymer, the lapsed time for the interface ormethacrylate and 1 Percent ammomllm between the clarifying supernatant liquidand settling 40 .hy h based on the Welghf i the monomer S solids to descend from the 90 milliliter to the milliliter tion t an Overall pp hunt on the amount of mark was measured. These times are reported as the ammonium hydro P h 15 pfi hh flocculation time's. by weight based on the welght of the monomer solu- The recipes to prepare several polymers and the meastion, urements of physical characteristics and flocculation 45 Pufglng the 111011011161 Solution of mhrbltory Y- times are reported as Examples 1-7. gen and Results Polymerization conditions M.B. l n Percent catalyst NH Tl T C tinie l so g NH mo, emp onv., Reference acrylatse K2820; Na S O exces s hrs. pH percent Vise lml. 2ml. 3m].

E l 1 .00 ,0015 N 40 *22-25 7.5 54.0 12333132 25. 6? .001; .0025 2?; 20 22-25 9.9 83 Example3 23, 7 .005 .0025 9.3 20 22-25 10.1 74 23.07 .005 .0025 18.1 20 "22-25 10.6 20 30 .01 .005 None 20 222% 7.0 81.9 30 .01 .005 0.1 20 22-25 7.22 86.5 30 .01 .005 1.0 20 *22-25 8.75 96.0

Room temperature.

It will be observed from Examples 2 through 3, as (3) polymerizing the resulting monomer system at a compared to Example 1, that superior results were obtempefah'll'e Wlthlh the range from q h 0 p to tained in regard to conversion of monomer to polymer, 111 the F of a p y h catalyst molecular weight and flocculation when the ammonia therefor whereby a high molecular weight, watersoluble polyelectrolyte is produced.

concentration was properly adjusted. The results from Example 4 demonstrate the eifect of an excessive concentration of ammonia. In this run the conversion of monomer to polymer was less than 20 percent.

In Example 5, 6 and 7, 30 percent by weight based on total solution weight of ammonium acrylate was polymerized in the presence of essentially none, 0.1 and 1.0 percent based on total solution weight of. ammonia. Although such small amounts of ammonium hydroxide 2. A method as in claim 1 and including the additional step of separating the polyelectrolyte from, the polymerizate, p g

3. A method as in claim 1 wherein the acrylate coricentration is within the range from about 20 to 40 percentby weight of the total polymerization system.

4. A method as in claim 1 wherein the acrylate is an ammonium salt of acrylic acid. 1

5. A method as in claim 1 wherein the acrylate is an gave no apparent advantage as regards polymer viscosity amm i lt f th li i L 6. A method as in claim 1 and including the additional step of introducing from about 1 percent by weight up to its saturation level of an alkali metal or ammonium inorganic salt to the polymerization charge.

7. A method as in claim 6 wherein the salt is sodium chloride.

8. A method as in claim 6 wherein the salt is sodium sulfate.

9. A method as in claim 6 wherein the salt is ammonium sulfate or ammonium chloride.

References Cited UNITED STATES PATENTS 3,405,106 10/1968 Scanley 260-80 3,472,243 10/1969 Wall 132-7 3,493,3500 2/1970 Volk 2l054 FOREIGN PATENTS JOSEPH L. SCHOFER, Primary Examiner C. A. HENDERSON, 1a., Assistant Examiner US. Cl. X.R.

204--l59.22; 2095; 2l054; 26078.5 R, 79.3 M, 

